[GiNaC-list] real_part and imag_part

[Richard B. Kreckel]

On 08/09/2017 09:12 AM, Vladimir V. Kisil wrote:
>>>>>> On Tue, 8 Aug 2017 20:15:07 +0200, Jan Rheinländer <jrheinlaender at gmx.de> said:
> 
>     JR> Hi, what is the logic here (example from ginsh)?
> 
>     >> real_part(sqrt(-3));
>     JR> sqrt(-3)
>     >> imag_part(sqrt(-3));
>     JR> 0
> 
>     >> real_part(sqrt(-1));
>     JR> 0
>     >> imag_part(sqrt(-1));
>     JR> 1
> 
>     The problems seems to be in CLN library, since for the
>   GiNaC::numeric object sqrt(-3), real_part() and imag_part() are simply 
>   calling cln::realpart() and cln::imagpart().

sqrt(-1) straightly evaluates to I, which works. But sqrt(-3) isn't a
numeric object. Rather, it is a power(-3,1/2).

Seems to me like the logic in power::real_part() and power::imag_part()
can be improved:
https://www.ginac.de/ginac.git/?p=ginac.git;a=blob;f=ginac/power.cpp;h=2619492805b58ad5d635f2d8fd67bfa0706c1281;hb=HEAD#l667

   -richy.
-- 
Richard B. Kreckel
<https://in.terlu.de/~kreckel/>